1. Field of the Invention
The present invention relates to a liquid discharge apparatus which discharges a liquid onto a target object from a liquid discharge nozzle formed on a liquid discharge head, particularly to a cleaning blade which cleans a liquid discharge head.
2. Description of the Related Art
An image forming apparatus in an ink jet printing system such as an ink jet printer is widely available in that its running costs are inexpensive and it is easy to print color images and to reduce the apparatus size. The ink jet printer is configured in which a very small quantity of ink is discharged from fine ink discharge nozzles arranged in an ink discharge area of a print head to record an image. In this type of ink jet printer, when it does not continuously operate to print for a long time and ink is not discharged from the ink discharge nozzles of the print head, the ink attached near the ink discharge nozzle in the ink discharge area due to the previous print operation sometimes evaporates, dries, thickens and hardens, causing the difficulty in normal ink discharge.
On this account, in traditional manners, a print head is cleaned in which a slightly hard rubber blade is pressed against the ink discharge area of the print head, and the blade is slid over the ink discharge area to wipe off the ink attached, thickened and hardened. In connection therewith, a technique is disclosed in which a plurality of blades is mounted on a shaft and rotated to further enhance the wiping effect (see JP-A-57-34969 (Patent Reference 1)).
In the cleaning of the print head using these blades, the flatness and the stiffness of a wiping member of the blade which rubs the ink discharge area of the print head affects the cleaning effect. More specifically, when the tip end area of the wiping member is not formed flat, even though the ink discharge area of the print head is rubbed, it is difficult to sufficiently wipe off thickened ink and waste such as paper dust attached to the ink discharge area. Furthermore, when the stiffness of the wiping member is not retained in the entire length touched to the ink discharge area, the wiping member slides over the ink discharge area at a predetermined pressure, deformation generated in the wiping member is unstable, and the wiping performance is unstable depending on the places in the wiping member.
Contrary to a serial scan head printing apparatus in which a print head provided with an ink discharge nozzle forms an image while it is moving in the print span direction of paper, particularly in a so-called line scan head printing apparatus in which ink discharge nozzles are arranged as matched with the print span of a paper sheet without moving a print head, the length in the print span direction of an ink discharge area of the print head in a nearly rectangular is also longer than that of the serial scan head printing apparatus. Therefore, in the line scan head printing apparatus, since the blade for cleaning the ink discharge area of the print head is longer as well, it is demanded that the flatness of the tip end of the wiping member is accurately secured in the entire length, and that the stiffness is secured as well. Furthermore, it is also demanded that the mounting accuracy is attained to mount such a long blade as it faces the print head.
Traditionally, this type of blade is fabricated in which a synthetic resin is cast into a predetermined mold for molding, it is punched out to form a wiping member, a supporting plate is perforated with a mounting hole for supporting the wiping member, and then the wiping member is mounted on the supporting plate formed of a metal or resin plate.
However, two corners in sectional form of the tip end of the wiping member to rub the ink discharge area are sometimes rounded, causing deteriorated cleaning performance of the ink discharge area in the width direction. Furthermore, for the distance between the mounting hole formed in the wiping member and the tip end part of the wiping member to be rubbed over the ink discharge area and for the flatness and the stiffness of the tip end part, the wiping member is demanded to have high accuracy in the entire length in the longitudinal direction. However, the stiffness of the wiping member is deteriorated when the wiping member is punched out, it tends to expand and contract in the plan direction. Therefore, the accuracy of the distance between the mounting hole and the tip end part of the wiping member is sometimes deteriorated, and the flatness of the tip end part might not be secured. Moreover, in order to solve such disadvantages, a method is proposed in which a mounting hole and the tip end of a wiping member is punched out before the other portions are formed when the wiping member is punched out (see JP-A-2001-10072 (Patent Reference 2)), which greatly restricts the fabrication process steps.
Furthermore, in the blade before, a number of slits are processed on the tip end of the wiping member which rubs over the ink discharge area, and the cleaning effect is improved by scraping off ink residues and foreign substances near irregular portions formed in the ink discharge area or by absorbing ink liquid into the slits with capillary attraction. These slits are formed when the wiping member is punched out.
However, as the slit width becomes narrower, more machining accuracy is demanded, and it is difficult to form the slits by punching out for the slit width in μm order. Furthermore, when the slit in narrow width is formed only by cutting the tip end part of the wiping member with a cutter, the cut areas of the adjacent wiping members are closely contacted with each other, or the pieces of the wiping members separated by the slits are overlapped with each other in places when the wiping member rubs the ink discharge area, causing places not wiped or no capillary attraction working. Moreover, the wiping member is mounted on the supporting plate to contract the wiping member because of the difference in the linear expansion coefficients thereof, and thus it is difficult to maintain the dimensional accuracy of the length and width of the slit in punching out.